Total Trihalomethanes

Disinfection byproducts (DBPs) are chemicals that form, during drinking water treatment and distribution, when naturally occurring organic matter reacts with chlorine or other disinfectants used to kill pathogenic organisms. The EPA has determined that Total Trihalomethanes (TTHM) are one of the chemical classes that must be monitored.
The Texas Commission on Environmental Quality (TCEQ) uses contract samplers to collect all TTHM samples used for compliance. TTHM samples are analyzed by the Lower Colorado River Authority or the Department of State Health Services and results are provided to the city and published online at TCEQ's Drinking Water Watch page. To read more about disinfection byproducts, visit TCEQ's webpage on DPBs.
Data is updated quarterly as sample results are received.

TTHM Results

To comply with the Stage 2 Disinfection Byproduct Rule, the rolling quarterly average at each sample site must be below .080 mg/L (80 ug/L).

To view sample results at each location, click "View Source Data" below the chart.

TTHM Chlorine Maintenance Special Samples

The North Texas Municipal Water District conducts chlorine maintenance throughout the water delivery system in February/March each year. Starting in 2018, the City of Plano began collecting samples to analyze disinfection byproducts during this time period. Samples are collected from the same 12 sites normally sampled plus the four pump stations. In 2019, Plano started conducting special sampling twice during the maintenance period. In 2020, samples were collected from the inlet and outlet locations at all four pump stations to monitor changes inside tanks. There was an error with the first set of samples collected at the Out location of Custer Pump Station and the In location of Stadium Pump Station. The chart below shows the received TTHM special sample results by location from both sample dates.